FIGS. 1A and 1B show a structure described in Patent Literature 1 as a conventional example of this type of dust cap. FIG. 2 shows a state in which the dust cap shown in FIGS. 1A and 1B is mounted to a connector (round connector).
A dust cap 10 is provided with rivet guide slots 10a for guiding rivets 15a of a connector 15 for smooth insertion when the dust cap 10 is mounted to and secured to the connector 15, and a rivet securing surface 10b having a planar structure that allows the rivets 15a to be secured when the dust cap 10 is secured to the connector 15. For dust proofing, a dust proof member 11, such as silicone rubber, is provided at an insertion end part 10c that the top of the connector 15 touches when the connector 15 is inserted.
To mount the dust cap 10 to the connector 15, the rivet guide slots 10a are aligned with the positions of the rivets 15a, the dust cap 10 is inserted into the connector 15, the dust cap 10 is pressed to the connector 15, and the dust cap 10 is rotated when the rivets 15a pass through the rivet securing surface 10b. With this operation, the dust cap 10 is secured by the rivets 15a and the rivet securing surface 10b due to the repulsive force of the dust proof member 11.